I purchased one of these in 20ga for my son since he is just getting started out.  We went to a skeet range to get a little practice in and we put 50 shells through it.  I noticed after about 20 shells that it became very hard to open, like I had to hold it across my knee to get it to open.

I didn't see anything on the primers that would indicate that the firing pins were dragging.  What else could be causing this?  I think we were using Federal Top Gun target loads.  Should we try a different shell manufacturer (like winchester AA ?).

Aside from this, we are very happy with the purchase.

P40

Most o/u and sxs actions are stiff brand new.  It will loosen up after 100 rounds or so.

Good to know.  Maybe when it warms up a little we can go put another 100 through it and see how it is then.

As others have said, a stiff opening/re-cocking is normal (and to a degree good) in a NEW break-open shotgun. It should loosen up and "wear-in" to where it becomes easier to open but still locks-up tight. Make sure the gun is lubed properly but NOT excessively.

Also, if you are using cheap "value pack" loads from Walmart (and other places) they can be part of the issue. The cheaper loads from Winchester (in particular) Remington and Federal can remain tight in the chamber after firing and make opening the action and extraction more difficult.

Try a box of Winchester AA or Remington STS (they run ~$8/box of 25) and see if you notice a difference.

I had a Browning 28ga do the same thing.A call to Browning service revealed that sometimes the grease they use for preserving and assembly may get hard/stiff.

They recommended sending it to a service center for repair  at their cost.

I couldn't bring myself to send the gun off as I had several $$$ in it.With the appropriate screw driver I disassembled(carefully doesn't even come close)  it and that is exactly what I found.

Cleaned it with solvents applied a very light coating of aviation grease and all is now good (for 5 yrs).

It is still tight but much improved, as someone else said it'll wear in.

I'd call CZ as a first step.

Good Luck

I shot a few rounds of skeet a while back on a very cold day and the grease that I was using froze which made it extremely difficult to open the action.

Once the gun warmed up, it was easy to open again.

Since then, I switched to Slip EWG and haven't had a problem again.